Bicarbonate is an indicator of arterial blood gas, reflecting the acid-base metabolic status of the body, including actual bicarbonate AB and standard bicarbonate SB. actual bicarbonate is the actual plasma bicarbonate level measured under actual conditions on an arterial blood specimen isolated from air, with a normal range of 22-27 mmol/L and an average of 24 mmol/L. standard bicarbonate is the bicarbonate level measured in arterial blood at 37°C, with a partial pressure of carbon dioxide at 40 mmHg and an oxygen saturation of 100%. The standard bicarbonate is measured in arterial blood at 37°C, partial pressure of carbon dioxide at 40 mmHg, and oxygen saturation at 100%, and there is no difference between the two in normal people. Generally speaking, if AB and SB are both normal, it means normal acid-base balance; if AB and SB are both lower than normal, it means metabolic acidosis loss; if AB and SB are both higher than normal, it means metabolic alkalosis loss; if AB is greater than SB, it indicates carbon dioxide storage; if AB is less than SB, it indicates excessive carbon dioxide excretion.